The present invention generally relates to tracking control apparatuses for rotary recording medium reproducing apparatuses, and more particularly to a tracking control apparatus which controls the tracking of a reproducing transducer element of a reproducing apparatus so that the reproducing transducer element accurately scans over a recorded track on a rotary recording medium which is played on the reproducing apparatus.
Conventionally, there is an apparatus reduced to practice in which video signals, for example, are recorded on concentric tracks on upper and lower recording surfaces of a rotary recording medium (hereinafter simply referred to as a disc) such as a magnetic disc. According to this apparatus, a pair of magnetic heads make contact with the respective upper and lower recording surfaces of the disc, and the video signals are recorded on the concentric tracks by alternately and intermittently moving the magnetic heads. In this type of an apparatus, a first head records a video signal of one field in one track turn on a first side of the disc while the disc rotates and the first head is stationary. Then, the first head is moved by two track pitches, and the stationary first head records in one track turn on the first side of the disc a video signal of one field which is obtained an interval of one field later. Thereafter, the first head is intermittently moved for every two track pitches and records the video signal of every other field in one track turn on the first side of the disc while the first head is stationary. Similarly, a second head records a video signal of one field in one track turn on a second side of the disc while the disc rotates and the second head is stationary. Then, the second head is moved by two track pitches, and the stationary second head records in one track turn on the second side of the disc a video signal of one field which is obtained an interval of one field later. Thereafter, the second head is intermittently moved for every two track pitches and records the video signal of every other field in one track turn on the second side of the disc while the second head is stationary. The second head records the video signals of those fields which are not recorded by the first head. Accordingly, the video signal is recorded in its entirety by the first and second heads which alternately record the video signal on the respective first and second sides of the disc. When the first and second heads intermittently move by two track pitches from respective outer peripheral positions and reach respective inner peripheral positions, the first and second heads move toward the respective outer peripheral positions by one track pitch and thereafter move intermittently at a rate of two track pitches. Hence, as the first and second heads move from the inner peripheral positions toward the outer peripheral positions, tracks are formed between the tracks which were formed as the first and second heads moved from the outer peripheral positions toward the inner peripheral positions. A recording and reproducing apparatus of this type is disclosed in U.S. Pat. Nos. 3,649,752 and 3,761,604, for example.
In the type of the recording and reproducing apparatus disclosed in the U.S. patents described above, each head is stationary and repeatedly scans over the same track turn during a still-picture reproduction mode. In this still-picture reproduction mode, the head position does not necessarily correspond accurately to the recorded track due to various causes such as contraction and expansion of the disc, mechanical precision of means for moving the head, and backlash of gears. When the head position is deviated from the recorded track in the radial direction of the disc, the width with which the head scans over the recorded track decreased and the level of the reproduced signal accordingly decreases. Hence, it is necessary to carry out a tracking control so as to correct the position of each stationary head so that each head accurately scans over the recorded track.
Conventionally, in order to carry out the tracking control during a reproducing mode of the recording and reproducing apparatus of the type described before so that each head accurately scans over the recorded track, a control signal for tracking control is recorded, at the time of the recording, beside the recorded track which is recorded with the video signal. During the reproducing mode, the control signal is reproduced and is supplied to a tracking control circuit of a tracking control apparatus which controls the head position so that each head accurately scans over the recorded track.
However, according to the conventional tracking control apparatus, heads exclusively for recording and reproducing the control signal and a circuit for processing the control signal must be provided in addition to the heads which record and reproduce the video signal. As a result, the construction of the recording and reproducing apparatus becomes complex, and the manufacturing cost of the recording and reproducing apparatus becomes high. In addition, because it is necessary to provide tracks for the control signal in addition to the tracks provided for the video signal, the recording density (recording surface utilization efficiency) of the disc with respect to the video signal is poor.